As a photoelectric conversion device for converting sunlight energy into electrical energy, there is a known thin-film silicon solar cell having a photoelectric conversion layer fabricated by forming thin films of a p-type silicon semiconductor (p-layer), an i-type silicon semiconductor (i-layer), and an n-type silicon semiconductor (n-layer) by using a plasma CVD method or the like. Thin-film silicon solar cells have the advantages that the area thereof can be easily increased, and only a small amount of material is used because the film thickness thereof is about one hundredth of that of crystalline solar cells. Therefore, thin-film silicon solar cells can be fabricated at lower cost than crystalline solar cells.
In general, a film formed mainly of amorphous silicon or a film formed mainly of crystalline silicon is used as a photoelectric conversion layer used for the thin-film silicon solar cell. For solar cells having an amorphous silicon film as the photoelectric conversion layer, it is known that impurities (oxygen and nitrogen) in the photoelectric conversion layer influence the cell performance (NPL 1).
PTL 1 discloses that there is a correspondence relationship between the Raman ratio (ratio of crystallization) of a crystalline silicon film and the cell efficiency, in a solar cell having a film formed mainly of crystalline silicon as a photoelectric conversion layer.